UiO-based Mixed Matrix Membranes for Efficient CO2 Separations.

Mixed matrix membranes (MMMs) containing UiO-type MOFs have shown excellent potential for CO2 separation processes due to their unique permeability and selectivity properties. However, while the performance of MOF-based MMMs has been widely studied, the effect of structural defects and polymer-filler compatibility are not yet fully understood. In this work, we systematically evaluate the CO2 separation performance of Pebax® MH1657-based MMMs incorporating 5 to 20 wt% of Zr-based MOF, including UiO-66, UiO-67, and two defect-engineered UiO-66 analogues, featuring extended linker (UiO-66_A) or cluster (UiO-66_F) vacancies. The structural, morphological, and thermal properties of the membranes were thoroughly characterised, with emphasis on correlating these features with gas transport performance. Single gas permeation experiments (CO2, CH4, H2) revealed that incorporating UiO nanoparticles within the matrix consistently enhanced CO2 permeability, reaching 145 Barrer for the 20 wt% UiO-66_F MMM, a 216.4% increase over the neat membrane. CO2/CH4 and CO2/H2 selectivities also improved upon increasing MOF loadings, with UiO-66_F achieving values of 25 and 18, respectively. This study provides insights for designing high-performance MMMs for CO2 separation applications, such as biogas upgrading and hydrogen purification.